State-owned Punjab National Bank has said in a statement that fraudulent transactions totaling $1.8 billion had been discovered in a Mumbai bank branch.

Indian media outlets have linked the scam to jeweler Nirav Modi. Authorities have not publicly blamed Modi for the $1.8 billion fraud, but say he is under investigation for cheating Punjab National Bank of $43 million by using fake bank “letters of understanding” to get loans.

The complaint says Modi and his relatives worked with bank employees to get the fake letters. News reports say the $43 million scam is part of the larger fraud.